Articulating torsional coupling

ABSTRACT

A constant velocity joint having driving and driven pivot arm segments coupled together with a pivotal bearing element provides high power density transmission through a large dynamic angle. The constant velocity joint may be configured for axial movement, such as a plunge capability, or may be a fixed center joint.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 15/304,241; filed Oct. 14, 2016, now U.S. Pat. No.10,156,265. U.S. patent application Ser. No. 15/304,241 is the U.S.National Phase of International Application PCT/US2015/055011 filed Oct.9, 2015 which designated the U.S. and that International Application waspublished in English under PCT Article 21(2) on Apr. 14, 2016 asInternational Publication Number WO/2016/057967. PCT/US2015/055011claims priority to U.S. Provisional Application No. 62/061,927, filedOct. 9, 2014. Thus, the subject nonprovisional divisional applicationclaims priority to U.S. Provisional Application No. 62/061,927, filedOct. 9, 2014. The disclosures of these applications are incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates in general to torque transmitting couplings. Inparticular, this invention relates to an articulating torsional couplinghaving a constant velocity output characteristic and an axial plungecapability.

Torque transmitting couplings are typically provided to accommodatepower transmission and angular misalignment between two rotating shafts.These couplings often use bearing or bushing elements to permitarticulation of input and output components as the shafts rotate.Different coupling designs exhibit particular operating and performancecharacteristics that limit their application to certain environments.The universal joint, also known as a Cardan or Hooke's Joint, is atwo-plane hinge joint having a first plane connected to an output shaftand a second plane connected to an input shaft. A journal cross definesthese planes, which are usually oriented at right angles. The journalcross typically terminates in four bearing elements that are mounted toyokes, each yoke lying in one of the first and second planes. A Cardanjoint is capable of providing a substantially high power density withina compact rotational envelope, referred to as the “swing diameter.”These joints are also durable and, because of the orientation of thebearings and sealing elements, are very damage tolerant, particularlywhen impinged upon by debris. However when operating at an angle, theCardan joint produces a non-uniform rotational output characteristicwhen provided with a uniform input characteristic. This non-uniformrotational characteristic results in the output shaft speeding up andslowing down twice every revolution, resulting in creation of vibrationdisturbances. The magnitude of this torsional disturbance increases withangle and rotational speed. Because of this condition, operating anglesof Cardan joints are often limited to keep torsional disturbances withinacceptable limits for a given application.

Other coupling designs are known that address the vibration disturbanceissue of a Cardan joint. These couplings utilize various designs toproduce a constant or near constant velocity ratio between the input andoutput shaft speeds relative to the misalignment angle. One broadcategory of constant velocity joints (CVJs) are the “ball-type” CVJs.These CVJs are the most common variety and rely on concentric input andoutput bearing races that transmit torque and accommodate angularmovement through ball bearing elements. By orienting the ball bearingelements within the homokinetic plane, these joints provide constantvelocity motion throughout their articulation range, which may be ashigh as 45 degrees, or greater. Some of these CVJs have a fixed centerwhile other designs are capable of accommodating axial movement. Themost common examples of these ball-type CVJs are the Rzeppa joint,cross-groove joint, and double offset joint. While these joints reduceor eliminate torsional disturbances, they can generate a higher amountof heat due to the ball bearing elements exhibiting both rolling andsliding motion as the joint rotates at an angle. This condition worsensas the torque, speed and angle operating parameters increase. Inaddition, the most common sealing element for these joints is anelastomeric boot that is often exposed to road debris. Once the boot istorn, these CVJs become quickly contaminated and exhibit a significantlyreduced operating life.

Both Cardan joints and ball-type CVJs have limited articulation angleswhich can restrict the design of the systems to which they are applied.For example, the range of suspension movement in a vehicle, particularlyan off-road vehicle, is limited to prevent over-angulation of thehalfshafts that connect the axle differential to the wheel ends. Othertypes of joints that exhibit constant velocity characteristics, such aslink-type couplings, have been known for some time. While these jointscan be made to articulate at relatively high angles, they suffer fromdurability issues. These issues are due to the component designs deemednecessary to permit high operating angles without articulated componentinterference. Thus, prior link-type CVJs have not provided the powerdensity necessary to permit their use in high load and space restrictedapplications, such as automotive powertrains. Thus, it would bedesirable to provide a torque transmitting coupling that provides aconstant velocity input to output ratio, accommodates a largearticulation angle, and exhibits increased durability with reduceddamage exposure.

SUMMARY OF THE INVENTION

This invention relates to torque transmitting couplings andparticularly, to an articulating torsional coupling having a constantvelocity output characteristic and an axial plunge capability.

A constant velocity coupling has a first central shaft and a pluralityof first pivot arms pivotally connected to the first central shaft. Theconstant velocity coupling further has a second central shaft and aplurality of second pivot arms pivotally connected the second centralshaft. An interconnecting bearing element couples each of the first andsecond pivot arms together such that torque and rotary motion aretransmitted through a joint angle. The plurality of first and secondarms of the constant velocity coupling define complementary curvaturesassociated with adjacent arm pivot connections that define a maximumjoint angle capacity within a joint swing diameter.

The constant velocity coupling may be configured where theinterconnecting bearing element is a spherical bearing element disposedin each of the plurality of first pivot arms. The plurality of secondpivot arms may each include a bore to receive an outer race portion ofthe spherical bearing element. In certain embodiments, theinterconnecting bearing element may be a spherical bearing element andone of the first and second pivot arms terminates in a yoke end thatengages opposite ends of an inner race portion of the spherical bearingelement. In other embodiments, the interconnecting bearing element maybe a clevis bearing element.

In certain embodiments, the constant velocity coupling may include afirst outer housing having a plurality of lugs connected to the firstcentral shaft. A second outer housing having a plurality of lugs isconnected to the second central shaft. The plurality of lugs of thefirst and second outer housings being in alignment with bores in thefirst and second central shafts. In other aspects of these embodiments,at least one of the first and second central shafts may be integrallyformed with the respective one of the first and second outer housings.Additionally, the plurality of first pivot arms may pivotally connectedto the first central shaft through a plurality of column bearingelements each compressed between one of the plurality of lugs and acorresponding face of the first central shaft. Alternatively, theplurality of first pivot arms may be pivotally connected to the firstcentral shaft through a plurality of threaded fasteners secured to thefirst central shaft. In another aspect of the invention, the pluralityof first pivot arms may be pivotally connected to the first centralshaft through a journal spider.

In certain other embodiments, the constant velocity coupling may includea centering device that is supported by the first and second centralshafts. In one aspect, the centering device is configured to restrictrelative extending and compressing axial movement of the first andsecond central shafts. Such a centering device may be a Cardan joint.Alternatively, the centering package of this aspect may be a first studterminating in a spherical end supported by the first central shaft anda second stud terminating in a spherical end supported by the secondcentral shaft. The first and second studs may be interconnected by asleeve. In other embodiments, the centering device may be configured torestrict relative compressing axial movement of the first and secondcentral shafts and permit relative extending axial movement of the firstand second central shafts. Still in alternative embodiments, thecentering device may be configured to generate an extending force on thefirst and second central shafts.

In another aspect of the invention, a constant velocity double joint mayinclude first and second constant velocity couplings. A first CVcoupling may include a first central shaft and a plurality of firstpivot arms pivotally connected to the first central shaft. The first CVcoupling may also include a second central shaft and a plurality ofsecond pivot arms pivotally connected the second central shaft. Aninterconnecting bearing element couples each of the first and secondpivot arms together such that torque and rotary motion are transmittedthrough a joint angle. The first CV coupling may also include a firstouter housing having a plurality of lugs is connected to the firstcentral shaft and a second outer housing having a plurality of lugsconnected to the second central shaft. The plurality of lugs of thefirst and second outer housings are aligned with bores in the first andsecond central shafts The constant velocity double joint also includes asecond CV coupling. The second CV coupling has a third central shaft anda plurality of third pivot arms pivotally connected to the third centralshaft and a fourth central shaft and a plurality of fourth pivot armspivotally connected the fourth central shaft. An interconnecting bearingelement couples each of the third and fourth pivot arms together suchthat torque and rotary motion are transmitted through a joint angle. Athird outer housing having a plurality of lugs is connected to the thirdcentral shaft and a fourth outer housing having a plurality of lugsconnected to the fourth central shaft. The plurality of lugs of thethird and fourth outer housings are aligned with bores in the third andfourth central shafts. A driven portion of the first CV coupling isconnected to a driving portion of the second CV coupling to transmittorque and rotary motion from a driving portion of the first CV couplingto a drive portion of the second CV coupling.

Various aspects of this invention will become apparent to those skilledin the art from the following detailed description of the preferredembodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of a constantvelocity (CV) coupling according to the invention.

FIG. 2 is an exploded view of the CV coupling of FIG. 1.

FIG. 3 is an exploded, perspective view of a second embodiment of a CVcoupling according to the invention.

FIG. 4 is a perspective end view of an outer housing and central drivingmember of the CV coupling of FIG. 1.

FIG. 5 is a perspective, cross sectional end view of an outer housingand central driving member of the CV coupling of FIG. 2.

FIG. 6 is a perspective view of a closed side of the CV coupling of FIG.1 in an angulated position.

FIG. 7 is a perspective view of an opened side of the angulated CVcoupling of FIG. 1.

FIG. 8 is a perspective view of a third embodiment of a CV couplingaccording to the invention.

FIG. 9 is an exploded view of the CV coupling of FIG. 8.

FIG. 10 is a perspective view of a fourth embodiment of a CV coupling inaccordance with the invention.

FIG. 11 is an enlarged, cross sectional view of an embodiment of aninterconnecting bearing and link arms of the CV coupling of FIG. 10.

FIG. 12 is a perspective view of a fifth embodiment of a CV coupling inaccordance with the invention.

FIG. 13 is a perspective view of the CV coupling of FIG. 12, shown incross section taken along line 13-13.

FIG. 14 is a perspective view of a sixth embodiment of a CV coupling inaccordance with the invention.

FIG. 15 is an exploded, perspective view of the CV coupling of FIG. 14.

FIG. 16 is a perspective view of an alternative embodiment of a centraldriving member and link arm subassembly.

FIG. 17 is a cross sectional view of the central driving member and linkarm subassembly of FIG. 16 taken along line 17-17.

FIG. 18 is a perspective view of yet another embodiment of a centraldriving member and link arm subassembly.

FIG. 19 is a cross sectional view of the central driving member and linkarm subassembly of FIG. 18 taken along line 19-19.

FIG. 20 is a perspective view of still yet another embodiment of acentral driving member and link arm subassembly.

FIG. 21 is a cross sectional view of the central driving member and linkarm subassembly of FIG. 20 taken along line 21-21.

FIG. 22 is a perspective view of another embodiment of aninterconnecting bearing and link arms.

FIG. 23 is a cross sectional view of the interconnecting bearing andlink arms of FIG. 22, taken along line 23-23.

FIG. 24 is a perspective view of an embodiment of a double joint CVcoupling assembly in accordance with the invention.

FIG. 25A is a side view of a load analysis layout of an embodiment of alink arm of a CV coupling in accordance with the invention.

FIG. 25B is a top view of the load analysis layout of FIG. 25A.

FIG. 26A is an outer housing cross section analysis showing a materialoptimization embodiment.

FIG. 26B is an outer housing cross section analysis prior to thematerial optimization of FIG. 26A.

FIG. 27 is an enlarged, perspective, cross sectional view of anembodiment of a fixed centering device.

FIG. 28 is a perspective, cross sectional view of a seventh embodimentof a CV coupling having an axial extension device in accordance with theinvention.

FIG. 29 is an enlarged view of a portion of the axial extension deviceof FIG. 28.

FIG. 30 is a perspective view of an eighth embodiment of a CV couplinghaving an anti-compression centering device in accordance with theinvention.

FIG. 31A is a geometric analysis through various planes of a two-armembodiment of a CV coupling in accordance with the invention.

FIG. 31B is a top view layout of the two-arm CV coupling of FIG. 31A.

FIG. 31C is a side view layout of the two-arm CV coupling of FIG. 31A.

FIG. 31D is an end view layout of the two-arm CV coupling of FIG. 31A.

FIG. 32A is a table of an embodiment of various design ratios for a CVcoupling in accordance with the invention.

FIG. 32B is a graph of strength factor vs. needle bearing separationfrom the table of FIG. 32A.

FIG. 33 is an illustration of a portion of a CV coupling having relativestructural dimensions based on a joint swing diameter.

FIG. 34 is a table of joint angle capacity versus a pivot arm curvaturedesign angle.

FIG. 35 is a plot of the tabulated values of FIG. 34.

FIG. 36 is an illustration of an embodiment of a centered CV couplingshowing a design plane separation dimensional relationship with thejoint swing diameter of FIG. 33.

FIG. 37A is a perspective view of a CV coupling, articulated at a 65degree angle, showing relative pivot bearing and arm interconnectingbearing and spatial relationships.

FIG. 37B is a schematic illustration of pivot arm design guide curvesfor a 65 degree joint angular capacity.

FIG. 37C is a schematic illustration of the relative size and spatialorientation of pivot and arm interconnecting bearings positioned at endsof the 65 degree guide curves.

FIG. 37D is an illustration of a pivot arm constructed within the 65degree guide curve of FIGS. 37B and 37C.

FIG. 38A is a schematic illustration of pivot arm design guide curvesfor a 20 degree joint capacity.

FIG. 38B is an illustration of a pivot arm constructed within the 20degree guide curve of FIG. 38A.

FIG. 39 is a graph comparing torque versus joint operating angle ofvarious types of torsional couplings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated in FIGS. 1 and 2, afirst embodiment of a link-type CV coupling, shown generally at 10. TheCV coupling 10 includes a driving portion 12 and a driven portion 14. Itshould be understood that the terms “driving” and “driven” areindicative of the direction of torque input and output. These terms arefor description purposes and are not intended to limit the structure ororientation of the CV coupling 10. The driving portion 12 is illustratedhaving an outer housing 16. The driven portion 14 also includes an outerhousing 18 that is similar to outer housing 16, though such is notrequired. The driving portion 12 and the driven portion 14 may sharemany common features and elements. These common features and elementswill be identified by the same reference numbers. These common elementswill be described in the context of either the driving or drivenportions, as best shown in the illustrated embodiments. The drivingouter housing 16 includes an attachment interface 20, illustrated as apiloted flange. However, the attachment interface 20 may be configuredas any type of attachment structure, such as a splined sleeve, splinedshaft, or other structure suitable for connecting powertrain componentstogether, which are known in the art. Similarly, the driven outerhousing 18 includes an attachment interface 22 that may be configuredsimilarly or differently than the attachment interface 20.

As shown in FIGS. 1, 2, and 4, the outer housing 16 includes a pluralityof lugs 24 that extend axially from the attachment interface 20. Theillustrated embodiment includes three lugs 24, though as few as one andas many as can be positioned around the outer housing 16 may beprovided. The lugs 24 are located radially from a central axis A by aradius R which, in part, defines the load capacity of the CV coupling.The lugs 24 are shown equally spaced about the circumference of theouter housing 16 and terminate in bores 26. Alternatively, the lugs 24may be unequally spaced about the circumference. In the illustratedembodiment, the lugs 24 have differing angled surfaces 24 a and 24 b inorder to permit large operating angles. These angled surfaces, however,may also be configured the same for embodiments that do not accommodatelarge operating joint angles.

A central shaft 28 extends axially from the outer housing 20. In theillustrated embodiment, the central shaft 28 is integrally formed withthe outer housing 16, though such is not required. The central shaft 28includes bores 30 that are axially aligned with bores 26. The bores 26and 30 define attachment points for pivot arms, described below. Thecentral shaft 28 further includes a thrust surface 32 that extendsaround each of the bores 30. The thrust surface 32 provides a torquereaction surface that maintains the orientation and position of thevarious bearing elements and components of the CV coupling 10. A similarthrust surface 34 is provided on the inner surface of each lug 24 andsurrounds the bore 26.

The driving portion 12 includes a plurality of pivot arms 36. As shownin the illustrated embodiment, each of the driving portion pivot arms 36is configured to be the same. The pivot arm 36 includes a pivot mount 38having a pivot bore 40 and a thrust face 42. A bearing element 44 may bedisposed in the pivot bore 40, which is then coaxially aligned with thebores 26 and 30. The bearing element 44 may be a singular element or aplurality of spaced apart bearing elements. The bearing element 44 maybe any suitable type of bearing element, whether providing sliding orrolling contact or a combination of both, such as for example a bushing,needle bearing, ball bearing, barrel-roller bearing and the like. Ajournal 46 extends through the bearing element 44 and into the bores 26and 30. In the illustrated embodiment, the journal 46 is configured as ashoulder bolt to provide a pivot axis and to fasten the pivot arm 36 tothe outer housing 16 and the central shaft 28. Other journalconfigurations that rely on additional attachment hardware are alsocontemplated to be within the scope of the invention. The pivot arm 36includes a body portion 48 that terminates in a connecting bore 50. Thebody portion 48 is configured such that the connecting bores 50 arealigned within the homokinetic plane of the CV coupling 10. The bodyportion 48 includes first and second leg sections 48 a and 48 b thatextend in radial and axial directions. The first and second leg sections48 a, 48 b are arranged such that the radial axis of the pivot base 38connects to the circumferential orientation of the plane of theconnecting bore 50 in the homokinetic plane. As will be explained below,the relative angular orientations of these leg sections determine theangular articulation capability and strength capacity of the CV coupling10.

In another aspect of the embodiment of FIGS. 2 and 5 the bearing element44 may be configured as a column member that is compressed between thethrust surface 34 of the lug 24 and the thrust surface 32 of the centralshaft 28 by the journal 46 (for example, configured as a bolt). In thisconfiguration, the bearing member may serve as an inner race about whichthe pivot arm 36 rotates. The compression of the bearing element 44between the two thrust surfaces increases the rigidity of the attachmentpoint of the pivot arm in reaction to an applied torque.

As shown in FIGS. 2 and 5, the driven portion 14 includes acomplimentary set of pivot arms 52 that are similar in arrangement topivot arms 36. Each of the pivot arms 52 include a pivot mount 54, aconnecting end 56, and a body portion 58. The pivot mount 54, asillustrated, may be configured to be the same as the pivot 38 includinga pivot bore 60 and a thrust face 62. The bearing element 44 may bedisposed in the pivot bore 40, which is then coaxially aligned with thebores 26 and 30 and operatively connected by journals 46. The connectingend 56 of the driven portion pivot arm 52, in the illustratedembodiment, supports a spherical bearing assembly, indicated generallyat 64. The spherical bearing assembly 64 includes an inner attachmentportion 66 that defines an inner race, or rotational support surface,and a mounting structure that attaches the spherical bearing assembly tothe connecting end 54. The inner attachment point 66 may be configuredas a bore that accepts a fastener 67, such as a bolt, to pivotallyretain the spherical bearing assembly, the pivot arm 36 and the pivotarm 52 together. In the illustrated embodiment, the inner attachmentpoint defines an axis having a generally radial orientation relative tothe axis A. The spherical bearing assembly 64 further includes an innerrace 68 a having a curved or spherical outer surface. The inner race 68is configured to be received within an outer race 68 b, received withinthe bore 50 of the driving pivot arm 36 to connect the driving and thedriven pivot arms 36 and 52 together. The outer race 68 b may have amating spherical inner surface. The pivot arm 36 pivots about thespherical bearing inner and outer races 68 a and 68 b relative to pivotarm 52 as the CV coupling revolves through 360 degrees at a joint anglebetween interconnecting shaft axes.

Referring now to FIG. 3, another embodiment of a CV coupling, showngenerally at 100 is illustrated. The CV coupling 100 includes two ends,similar to the CV coupling 10 above, which will be described in thecontext of a driving portion 112 and a driven portion 114. The drivingportion 112 and the driven portion 114 are illustrated having outerhousings 116 and 118, respectively. The outer housings 116 and 118 aresimilar in configuration, though such is not required. The outer housing116 includes an attachment interface 120 that may be any structureconfigured to permit attachment of the outer housing to a matingdriveline component, such as a companion flange, splined member (fixedor sliding), and the like. The outer housing 116 further includes aspider mounting surface 122 that locates and supports the attachment ofa journal spider, shown generally at 128. The outer housing 116 furtherincludes a plurality of lugs 124, which are shown in the illustratedembodiment as being three lugs 124, equally spaced about thecircumference, though such is not required. Each lug 124 includes amounting bore 126.

The journal spider 128 includes a central body 130 having a plurality ofthrust surfaces 132 and a pivot journal 134 that extends radially fromeach thrust surface 132. The pivot journals 134 are configured to bealigned with the mounting bores 126. In one embodiment, the pivotjournals 134 may be configured to accept a fastener 135, such as forexample a bolt or snap ring arrangement (i.e., removable) or rivet,weld, staked attachment and the like (i.e., permanent attachment) toretain the pivot journal 134 to the lug 124. The specific illustratedembodiment shows three, integrally-formed thrust surface and pivotjournal structures (132 and 134) disposed equidistantly; however, thenumber and spacing may be varied. The thrust surface 132 may function inthe generally same manner as thrust surface 32, described above. In oneembodiment, the pivot journals 134 may be formed as an inner racesurface that extends through a bore 140 formed through a pivot mount 138of a pivot arm 136. In one embodiment, the pivot mount 138 may functionas an outer bearing race and may further include one or more rows ofrolling element bearings, such as conventional needle rollers may bedisposed along the surface of the pivot journal 134. The pivot mount 138may further include a thrust surface 142 that engages the thrust surface132. The pivot arm 136 further includes a body portion 148 that isillustrated as being angled in at least two planes, similar to bodyportion 48 described above. The body portion 148 terminates in aspherical bearing assembly 164, similar to spherical bearing assembly64, described above. In the illustrated embodiment, a spider mount 144,shown as a flange, extends between the central body 130 and the spidermounting surface 122. The spider mount 144 is configured to locate andcenter the journal spider relative to the outer housing 116. Anysuitable mounting arrangement, such as a splined shaft that mates with asplined bore through the body 130, mating tapers, and the like may beprovided.

The driven portion 114 is illustrated having an outer housing 118 and ajournal spider 128 that are the same or similar to those of the drivingportion 116, though such is not required. The driving portion 114further includes driven pivot arms 166 that include a pivot mount 168having a thrust surface 170 and a pivot bore 172. The pivot arms 166also include a body portion 174, similarly configured to the bodyportion 148 of the driving portion 112, that terminates in a connectingend 176 having a bore 178 formed therethrough. The connecting bore 178is configured to receive an outer race portion of the spherical bearingassembly 164 such that torque, rotational and angular motion from thedriving portion 112 are transmitted to the driven portion 114. Afastener 165, illustrated as a bolt, may be provided to retain theassembled connection of the spherical bearing assembly and the pivotarms 136 and 166 together. Referring now to FIGS. 6 and 7, theembodiment of the CV coupling 100, described above, is shown in anassembled and articulated condition.

Referring now to FIGS. 8 and 9, there is illustrated another embodimentof a CV coupling, shown generally at 200. In the illustrated embodiment,the CV coupling 200 includes a driving portion 212 and a driven portion214. The driving and driven portions 212 and 214 include outer housings216 and 218 that are generally the same as outer housings 16 and 18,described above. Connected to the driving portion outer housing 216 area plurality of pivot arms 236. Similar to the pivot arms describedabove, pivot arm 236 includes a pivot mount 238 having a pivot bore 240formed therethrough and a thrust surface 242. A body portion 248 extendsin a plurality of relatively angled planes from the pivot mount 238. Thebody portion 248 of each pivot arm 236 terminates in a clevis receiver250. The clevis receiver 250 includes a clevis pivot bore 252 that mateswith a clevis 254. The clevis 254 includes a stem end 256 and a yoke end258. The stem end 256 is supported for rotational and axial movementrelative to the pivot arm 236 about an axis (not shown) extendingthrough the clevis pivot bore 252. Rolling or sliding bearing elements(not shown) may be provided between the stem end 256 and the clevispivot bore 252 if desired.

The driven portion 214 includes a plurality of pivot arms 260, that areillustrated as the same or similar to pivot arms 236, though such is notrequired. The pivot arm 260 includes a pivot mount 262 having a pivotbore 264 extending therethrough and a thrust surface 266. A body portion268 extends is a plurality of angled planes from the pivot mount 262 andterminates in a link receiver 270 having a link pivot bore 272 extendingtherethrough. A hinge link 274 includes an eyelet end 276 and a pivotstem 278. The eyelet end 276 includes thrust surfaces 280 which arereceived within the yoke end 258. The eyelet end 276 is pivotallyretained therein by a fastener, such as a pin, rivet, bolt and the like(not shown). The hinge link pivot stem 278 may be supported within thelink pivot bore 272 in a similar manner to the clevis stem end 256,described above. As the CV coupling 200 rotates through a 360 degreerevolution and through a joint articulation angle, the clevis 254 andhinge link 274 rotate relative to their respective pivot bores and theeyelet end 276 hinges within the clevis yoke 258. The thrust surfaces280 engage the inner surface of the clevis yoke 258 to transmit motionfrom the driving portion 212 to the driven portion 214.

Referring now to FIGS. 10 and 11, there is illustrated anotherembodiment of a CV coupling, shown generally at 300. Similar to the CVcoupling embodiments described above, the CV coupling 300 includes adriving end 312 and a driven end 314. The driving and driven ends 312and 314 include outer housings 316 and 318 the may be configured in asimilar manner to the various outer housing embodiments describedherein. The driving end 312 includes a plurality of pivot arms 320. Thepivot arms 320 include a pivot mount 322, configured similarly to thevarious pivot mount embodiments described above. A body portion 324extends from the pivot mount 322 at a plurality of relatively angledplanes and terminates in a swivel hinge end 326. The swivel hinge end326 includes a swivel receiving bore 328 that accepts a spherical swivelbearing assembly 340. In one embodiment, the swivel bearing assembly 340includes a spherical inner race 342 and a mating outer race 344 thatcurves around the outer diameter of the inner race 342. The sphericalinner race 342 includes a bore 346 formed therethrough. The bore 346 mayinclude rolling or sliding bearing elements that also engage a clevispin 348 a. The swivel hinge end 326 is configured to be received withina clevis end 350 of a driven pivot arm 352. The driven pivot arm 352 maybe configured similarly to driving pivot arm 324. The clevis end 350includes a yoke 354 having bores 356 that engage the spherical innerrace 342 and accept the clevis pin 348 a. A crush sleeve 348 b may beprovided to maintain a spaced apart relationship of the ears of yoke 354and may serve as a race for the rolling or sliding bearing elementswithin the spherical inner race 342. The crush sleeve 348 b may alsoserve as a structural member to increase rigidity of the joint. As theCV coupling 300 rotates through 360 degrees at an articulated jointangle, the spherical inner race 342 pivots within the outer race 344. Inone embodiment, the spherical inner race 342 may also rotate within theouter race 344 about an axis that is in line with the clevis pin 348 a.In another embodiment, the spherical inner race 342 may rotate about theclevis pin 348 a and relative to the yoke 354. The clevis pin 348 a maybe any suitable fastening structure that retains the driving and drivenpivot arms 320 and 352 and permits rotation of the swivel bearingassembly 340. In one embodiment, the clevis pin 348 a may be a threadedfastener, such as a bolt and nut, or alternatively a rivet that permitsa clamping force to be applied to the crush sleeve 348 b.

Referring now to FIGS. 12 and 13, there is illustrated an embodiment ofa CV coupling, shown generally at 400. The CV coupling 400 includes adriving portion 402 and a driven portion 404, illustrated in a similarconfiguration to the CV coupling 300, above. The driving and drivenportions 402 and 404 include outer housings 406 and 408, respectively.The outer housings 406 and 408 are illustrated having a similarconfiguration, and will be described in the context of outer housing406. The outer housing 406 includes a plurality of lugs 410 and acentral shaft 412. The central shaft 412 includes a plurality of bores414 that are aligned with bores 416 formed in the lugs 410, similar tothe embodiments described above. The central shaft 412 further includesa centering bore 418 formed along axis A. The centering bore 418 isconfigured to support a first portion 420 of a centering device 422,illustrated as a Cardan joint yokeshaft. The outer housing 408 of drivenportion 404 is configured as a mirror image of the driving portion outerhousing 406, including the central shaft 412 having a centering bore424, defining a second axis B, and a second portion 426 of the centeringdevice 422. The first and second centering portions 420 and 426, whenconfigured as Cardan yokeshafts, are connected together by a universaljoint 428. One or both of the Cardan yokeshafts 420 and 426 may berotatably mounted and axially constrained to the respective centralshaft centering bores 418 and 424. The centering device 422 maintainsthe spatial intersection of axes A and B as the joint articulatesthrough a changing joint angle. In the illustrated embodiment, thecentering device 422 is configured to prevent relative axial movement ofthe driving portion 402 relative to the driven portion 404, as the CVcoupling 400 articulates through the operating angle. In certain cases,the centering device components may not need be rotatably mounted.Additionally, for typical joint construction configurations, a Cardanjoint would be substantially modified and can be taken to highmisalignment angles, such as about 90 degrees, and still have thenecessary thrust capabilities. All other types of CV centering deviceswill likely substantially decrease/limit joint angle capability.

In one embodiment, the Cardan yokeshafts 420 and 426 may be supported bybearings within at least one of the central shaft centering bores 418and 424. The rotational support of one or both of the yokeshafts 420,426 permits the centering device 422 to rotate independently of thecentral shafts. As the driving and driven portions 402 and 404articulate the operating angle may exceed the angle capacity of thecentering device 422. This over angulation of the centering device 422may cause the device to stop moving relative to the support. Thus, thebearing supports in the bores 418, 422 permit the driving and drivenportions to continue operation without interference from the centeringdevice. In addition, the support bearing may further permit thenon-uniform rotational characteristics of a Cardan centering device frominteracting with the central shafts. Alternatively, the centering deviceneed not be a Cardan joint but may be any fixed coupling element, suchas a fixed center cross groove CV joint, a fixed center double offset CVjoint, or any other fixed center, angle accommodating device.

Referring now to FIGS. 14 and 15, there is illustrated an embodiment ofa CV coupling, shown generally at 500. The CV coupling 500 does notinclude outer housings but may be used in conjunction with features ofthe various embodiments of the CV coupling, described above, includingthe outer housings. The CV Coupling will be described in conjunctionwith a driving end 502 and a driven end 504. The driving end 502 of theCV coupling 500 further includes a central shaft 506 and a plurality ofpivot arms 510, 512, and 514. The driven end 504 includes a centralshaft 508 and a plurality of pivot arms 516, 518, and 520. The pivotarms 510-520 include interconnecting bearing elements, illustrated asclevis and hinge link elements similar to the clevis and hinge linkelements 254 and 274, described above. It should be understood that anyof the various pivot arm interconnecting structures may be applicable tothis embodiment. The center of the interconnecting elements lie in thehomokinetic (HK) plane. The central shaft 506 includes a plurality ofbores configured to pivotally support the pivot arms 510, 512, and 514.The bores 522, 524 and 526 are longitudinally offset along thecenterline of the central shaft 506. The pivot arms 510, 512, and 514vary in length from the homokinetic plane to the respective pivot bores522, 524, and 526 by the amount of the offset of the bores. Thus, pivotarm 510 locates in pivot bore 522 and has the shortest length. Pivot arm514 locates in pivot bore 526 and has the longest length. Pivot arm 512locates in pivot bore 524 and has a length about midway between thepivot arms 510 and 514. These length variations permit the centerlinesof the interconnecting bearing elements to lie substantially within thehomokinetic plane, thus permitting constant velocity speed operationthrough the angular articulation range. Similarly, central shaft 508includes offset pivot bores 528, 530, and 532. Pivot arms 516, 518, and520 are configured with length variations that correspond to the pivotbore offset distances. As illustrated, pivot arm 516 is the shortest armand is supported by pivot bore 528. Pivot arm 518 has an intermediatelength and is supported by pivot bore 530. Pivot arm 520 is the longestof the three and is supported by pivot bore 532. In the illustratedembodiment, the three lengths of the pivot arms are the same between thedriving and the driven portions 502 and 504. Thus, for example, pivotarm 514 is the same length as pivot arm 520.

Referring now to FIGS. 16-21, there are illustrated various embodimentsof a central shaft having different pivot arm mounting arrangements.Though illustrated in conjunction with embodiment of the central shaft506 having offset pivot bores, these embodiments may be used inconjunction with other configurations of the central shaft, describedherein. FIGS. 16 and 17 illustrate an embodiment of a central shaft 600having a pivot arm 602 mounted onto a through shaft 604 that issupported by two bearing elements 606. The pivot arm is connected by wayof a pinch connection 608. FIGS. 18 and 19 illustrate an embodiment of acentral shaft 620 and a pivot arm 622. The pivot arm 622 includes anintegrally formed pivot shaft 624 that is supported on the central shaft620 by bearings 626. FIGS. 20 and 21 illustrate another embodiment of acentral shaft 640 having a plurality of pivot support trunnions 642extending therefrom. Each of the trunnions 642 pivotally supports apivot arm, such as pivot arm 644. The pivot arm 644 includes a bearingend 646. The bearing end 646 may be a bore that receives a bearing orbushing assembly, such as needle roller assembly 648, which is disposedabout the trunnion 642. The pivot arm 644 and needle rollers 648 areretained by an end cap 650.

Referring now to FIGS. 22 and 23, there is illustrated an embodiment ofa pair of pivot arms 702 and 704 coupled by an interconnecting sphericalbearing 706. This embodiment is similar to the CV couplings 10 and 100,described above. The interconnecting spherical bearing 706 includes aball stub portion, shown generally at 708. The ball stud portion 708includes a ball end 710 and a stud end 712. The stud end 712 may betapered to engage a mounting bore 714 and be retained by a retaining nut716. The ball end 710 is retained in a spherical outer race 718 and maybe configured as a relubricatable bearing element having a zerk fitting720.

Referring now to FIG. 24, there is illustrated an embodiment of a doublejoint, shown generally at 800. The double joint 800 includes a first CVcoupling 802 connected to a second CV coupling 804. Any of theembodiments of CV couplings described herein may be provided as thefirst and second couplings 802 and 804. In one aspect, the double jointmay be a self-supporting joint where each of the CV couplings includes acentering device, such as that shown in FIGS. 12, 13, and 27 forexample. In another aspect, the double joint may omit the centeringdevices form one or both of the couplings. In this case the joint can beused to connect to rotating shafts with non-intersecting axes. Asillustrated, coupling 802 is attached to coupling 804 by connecting thetwo end outer housings. Alternatively, the two end outer housings may beformed as a single structure.

Referring to FIG. 39, there is illustrated a comparative graph of torqueversus operating angle for various types of torque transmittingcouplings, and various embodiments of the CV coupling (also termed the“Harris” joint) according to the invention. The maximum operating anglelimits for each kinematic coupling may be based on a variety of factors,such as bearing life, rotational speed, and component strength, to namea few. It should be noted that the Rzeppa curve represents a compositeof several different types of commonly used CV couplings, such as theRzeppa Joint, Cross Groove joint, and Double Offset Joint. It may beobserved that the Harris joint has a much higher practical angular uselimit, along with a less drastic torque degradation as a function ofjoint angle. Both of these factors will help lift constraints typicallyused in powertrain design to provide better performing and moreefficient systems.

The various embodiments of the “Harris” coupling according to theinvention described above, consist of three primary component types thatform each half of the coupling:

-   -   1. Articulating arms (one or more pairs), three pairs allow for        a self centering, very high torque capacity high angle compact        coupling.    -   2. The central input and output shafts from which the arm pivot        shafts extend radially to attach to the outer housing.    -   3. The outer arm pivot bearing shaft housing support member.

The outer housing can be an integral part of the central member or anindividual bolt on member. The ability of the Harris coupling to haveindividual bearing seals without a boot requirement is especially usefulfor very high angle applications where boots are prone to fail. Incertain embodiments, however, the Harris coupling may include a boot inlieu of individual bearing seals or in addition to these bearing sealfor added contamination resistance. The rigidity of the individualcomponents keeps the arm spherical bearing centers lying substantiallywithin the homokinetic plane under operating conditions. Significantdeviation of these centers from the homokinetic plane may cause velocityfluctuations that can result in drive pulsations.

The Arm Assemblies

While not exhaustive, some select primary design considerations for thearm assemblies include the following:

-   -   1. Beam strength    -   2. Torsional strength    -   3. Pivot bearing spacing and size    -   4. Spherical bearing size

A numerical analysis of these design considerations is based on a forceanalysis for a specific implementation of an embodiment of the Harriscoupling based on a 4.75 inch outer diameter coupling loaded to 2000foot pounds of torque. Referring to FIGS. 25A and 25B, there areillustrated a side view and a top view, respectively, of a typical armhaving a pivot axis −Z— and a spherical bearing (or Clevis) having acenter, P. In a particular aspect of the invention, an example of actualdimensions are described below. As shown in the top view of FIG. 25B,the arm includes a bend that offsets the bearing center, P from thepivot axis Z. This bend permits the operating angle of the joint to bemaximized while minimizing the overall axial length of the assembly.Similarly, when maximizing the operating angle to approach an outerenvelope of about more than 80°, other portions of the arm between theinterconnecting bearing support and the arm base pivot connection mayinclude contours. Such contouring is provided to smooth load flow (i.e.,stress distributions and strain concentrations) through the arm andavoid component collisions.

As shown in FIGS. 25A and 25B, some exemplary arm dimensions, as used inthe load calculations include the following:

-   -   A=1.5 inches coupling rotation        to P (side view)    -   B=1.0 inch pivot bearing center distance (½″ wide bearings)    -   C=1.5 inches total length of arm pivot bearing hole    -   D=1.25 inch arm bend offset from coupling rotation        to P (top view)    -   E=0.60 inch    -   F=1.20 inch bearing support housing OD    -   G=1.20 inch arm section thickness    -   T1, T2 are illustrated as thrust bearing faces

Local arm loads, in pounds, and the approximate force directions, whichvary with coupling angle, are calculated from the dimensions of FIGS.25A and 25B as follows:

-   -   F1=5333 lbs.; F2=8000 lbs.; F3=8000 lbs.;    -   F4=5333 lbs.; F5=6666 lbs.; F6=6666 lbs.        As shown in FIGS. 25A and 25B, the arms experience both a high        bending (beam) load and a torsional load due to the offset of        the spherical        (dim. D) from the pivot axis Z.

In one embodiment, the ratio of A/B may be in the range of (approx.) 1:1to 1.5:1. In another embodiment, the ratio may be dependent onmaximizing the “B” dimension.

Central Driving Member

The central driving member, also described above as the central shaft 28and the related various embodiments, provides a mounting connection fortorque transmission between the input or output shafts and therespective driving or driven link arms. In one embodiment, the centraldriving member is a separate component from the outer housing. Inanother embodiment, the central driving member may be the only supportconnection between the link arms and the input or output shafts.

As shown in FIG. 25A, driving loads are transmitted from one half of thecoupling to the other half via the pivotal arm connection “P.” The threearticulation points shown in conjunction with the pivot arm connections,P equate to six “arms” or arm segments. The arm force diagram shows thatthe load at “P” produces an internal torque between the central memberand the housing, also termed outer housing 16, 18 and the variousembodiments thereof. The arm reaction forces are accounted for bymaximizing the torsional stiffness of both the central member and theouter housing. Increasing the torsional stiffness reduces deflectionsand added bearing loads from skewing or pinching of bearing elementsthat can reduce bearing life.

FIGS. 26A and 26B show a composite cross section of the outer housingand joint central member. The lower drawing (FIG. 26B) illustrates anembodiment having a constant diameter shaft joining the mounting planeto the arm pivot axes plane. The upper drawing (FIG. 26A) illustrates anembodiment having a torsional strength and beam strength optimizedconfiguration. The generally conical surface, S is a surface ofrevolution about the input shaft axis, Z. In one embodiment, the maximumouter diameter (OD) of the conical surface, at all axial cross sections,is limited by arm interference when operating a maximum joint angles.Both FIGS. 26A and 26B show outer housings having the same materialthickness, t, which in one exemplary embodiment may be t=0.25 inches,though other material thicknesses may be used. Since the torsionalstiffness is a function of diameter to the 4^(th) power, the shape ofthe conical surface, S, is capable of providing up to a potential 50%improvement of torsion stiffness with an appropriate I.D. hole. Inaddition, the conical shape may also provide up to a 100% increase inbeam strength and a net weight reduction. In certain embodimentsdescribed herein, the central shaft optimization may be controlled bythe shape of the link arm.

Outer Housing Optimization

The outer housing experiences loads that originate at the “A” attachmentpoint to the arm pivot bearing shaft outer ends. These loads are bothcircumferential at right angles to the hub rotational axis, and in theaxial direction, especially when the joint is operating at a maximumangle.

Referring again to FIGS. 26A and 26B, the diagram shows an optimizedouter member cross-section, shown generally at 900, (FIG. 26A) throughthe housing centerline (

) above the joint

, and a non-optimum outer housing, shown generally at 950, below thejoint

(FIG. 26B). By angling the inside of the outer housing surface 902 andthe outside surface 904, the rigidity of the housing is markedlyimproved in all directions, and it is lighter. As in the case of thecentral member the arms partly determine the position and shape of theangled surfaces 902 and 904.

In one embodiment, the torsional stiffness of the housing is about 5times the stiffness of the central member. The torsional stiffnessfurther impacts the spatial accuracy of the arm pivot shafts and thespherical joint center locations when highly loaded.

Centering and Anti-Plunge Devices

In certain embodiments of the Harris CV coupling, the joint exhibits anaxial plunging or axial length changing capability. In otherembodiments, the use of additional components restricts or inhibits theaxial movement. In certain embodiments, one limit on the total amount ofaxial plunge distance is component interference. By restricting theamount of axial plunge, the joint is kept away from its mechanicallimits to prevent wear and potential damage.

In certain applications, the driver and driven shafts/hubs are fixedwithin bearings that are axially constrained and therefore the jointwill run in one position without the need for any centering device oraxially constraining member. In other applications, it may be beneficialfor the joint to be self-limiting with respect to axial plunge. As shownin FIGS. 27-30 and described below, several embodiments of centering andanti-plunge structures keep the joint away from its axial displacementlimits. The various embodiments of centering and anti-plunge structuresmay be varied and may depend on the specific application. Some of theembodiments described herein limit compression only, some induceextension (springs and pneumatic plungers), and others limit both theextension and compression of the joint.

Fixed Centering Devices for Limiting Extension and Compression

In many automotive applications a rotating axle will consist of twojoints coupled by a shaft. Typically, a linkage determines theseparation distance of the joints and varies as the linkage moves. Thislayout typifies a front wheel drive corner module where one of thejoints typically does not extend or compress and the other is free toplunge therefore accommodating the length change needed. In the case ofthe fixed joint. a centering mechanism that does not allow the joint toplunge aids in providing maximum angulation because all components tendto be positioned optimally for maximum misalignment. In a frontwheel-drive application, where the outboard joint is subject to thelarger angular articulations and often times pivots about the kingpincenterline, typically a fixed joint is positioned on the outboard sideof the shaft and the plunging joint on the inboard side. Two mechanicalsolutions for limiting both axial compression and extension are listedbelow.

Referring back to FIGS. 12 and 13, a Hooke Joint or Cardan Joint(u-joint) such as u-joint 428, may be utilized as a fixed centeringstructure. As shown, the u-joint may be mounted between the centralmembers of the hubs. In one embodiment, the u-joint may be supported bybearings or bushings within the hubs to accommodate angular velocityvariations inherent with u-joints operated at an angle.

Referring to FIG. 27, an alternative embodiment of a centering package,shown generally at 1000, may be provided instead of a universal joint.In the embodiment of FIG. 27, a stud 1002 terminating in a spherical end1004 is attached to each central driving member. The spherical ends 1002extend into a sleeve 1006. A separating bushing 1008 contacts eachspherical end 1002 to define a spaced apart relationship between the twoCV couplings. An open end 1010 of the sleeve 1006 is closed around therear surface of the spherical end 1002, either by an upsetting orcrimping process or by way of a mechanical stop, such as a collar orsnap rings 1012.

Extension Inducing Devices

Referring now to FIGS. 28 and 29, there is illustrated an exemplaryextension device. In some applications, providing a force to extend thejoint can keep another component downstream pressed against a rigidsurface. This results in a specific operating location, provided anyopposing force does not overcome the extending mechanism. Using theautomotive halfshaft as an example, the inboard rear joint could have arigid bottoming device and the outboard joint could be loaded with aspring or pneumatic plunger which keeps the coupling shaft incompression holding the inner bottoming device in contact. In thesecases a spring, spring loaded plunger, or pneumatic/hydraulic plungerwould be located in the central member of the hubs.

As shown in FIGS. 28 and 29, an extension centering device 1100 includesa plunging end 1102 and a fixed end 1104. The fixed end 1104 may includean adjustment portion, such as a threaded section 1106 to provide anoffset of a first contact head 1108 from the joint center or toestablish a solid surface at the homokinetic plane. The plunging end1102 includes a bore or cylinder 1110 and a plunger 1112 disposed in thebore 1110. The plunger 1112 includes a piston 1114 and a second contacthead 1116. In one embodiment, the second contact head 1116 is rounded atthe end such that rolling contact between the first and second contactheads 1008 and 1116 occurs as the joint articulates. The bore 1110 maybe hydraulic fluid, or gas and may be pressurized or at an atmosphericpressure when the joint is in an axial rest position, i.e., not axiallydisplaced. The plunger 1112 may be retained within the bore 1110 by asuitable retention mechanism, such as a snap ring or a retainer plate1118, as shown in FIG. 29.

In addition to axially extending mechanisms that emerge from the centralmember, it is possible to attach torsional springs to the arm pivotswhich would torque the arm about its pin resulting in either anextending force or a retracting force if desired. It is noteworthy thatin certain automotive applications, a specific operating axial locationis not always necessary if the joint does not operate near its maximumallowable angle. The interconnecting shaft extending between two Harrisjoints can be free to axially move or float, as is the case with certaintypes of constant velocity joints. When two Harris joints are used on acommon shaft centering forces counterbalance each other such that theshaft dynamically finds its center position. To aid in centering, twospring loaded (or pneumatic) plungers could be used on both sides of theaxle to aid centering but still allow float.

Anti-Compression Devices

Referring now to FIG. 30, there is illustrated an exemplaryanti-compression or anti-plunging device, shown generally at 1200. Inone embodiment, the anti-plunging device, configured to resistcompression of the input and output joint halves, comprises a firstshaft 1202 attached to one of the hubs central member and a second shaft1204 attached to the other hubs central member. In the illustratedembodiment, the first shaft 1202 is configured with a domed contactsurface, and the second shaft is configured with a flat surface.Alternatively, both first and second shafts 1202 and 1204 may have domedsurfaces. The first and second shafts 1202 and 1204 are supported bybearing elements 1206, though such is not required. The shafts areconstrained from compression deflections but are free to move away fromone another. In one embodiment, the shafts 1202 and 1204 are positionedwith a specific bottoming point that is in line with the homokineticplane when the joint is positioned at least with no joint angle.Alternatively, the bottoming out point or compressive stop point may beany position between the linear range of movement of the joint. In theillustrated embodiment, the joint will pivot about a single point whenheld at the compressive stop position. This point may be the center ofthe radius on the domed shaft portion of the anti-plunge device.Alternatively, the pivot point at the compressive stop point may be theflat contact surface of the second shaft 1204. The bottoming stops canbe integral to the central members of the hubs, supported by bearings asillustrated, or fastened to the central members. As mentioned above inrelation to extension inducing devices, it may be beneficial to specifya limit to axial movement of the shaft, i.e., a backlash, and yet stillpermit the shaft to float between its limiting stops on both ends.

Basic Joint Geometry

Referring now to FIGS. 31A-31D, a two arm joint design illustrates thebasic geometry of the Harris Coupling and the relative association ofthe various torque-transmitting components. The input and output shaftsS1 and S2 are shown pivotally connected at pivot point Z0, which iscoincident with the homokinetic plane. Other embodiments may not includethe pivot point Z0. The input shaft S1 rotates about the input axis C1and the output shaft S2 rotates about the output axis C2. Thearticulating arms A1 and A2 and their associated pivot point P1represents the various embodiment of the articulating arms describedabove. The pivot point P1 coincides with the bearing element thatinterconnects the arms of the embodiments described above. The pivotpoint P1 is configured to permit articulation of the arms A1 and A2 asthe joint rotates through 360 degrees at any angular orientation, θ(theta), within the joint angle capacity. The arms A1 and A2 rotateabout axes AX1A and AX2A. The axes AX1A and AX2A of arm pair A1 and A2are substantially perpendicular to the input and output shaft axes C1and C2, respectively.

The basic joint geometry and load capacity may be further defined by thefollowing dimensions. Distances B1 and B2 represent the offset of thearm centerline axes AX1A and AX2A from the homokinetic plane. In theembodiments illustrated herein, the offset distances B1 and B2 aresubstantially equal in length at all joint angles. Distances D1 and D2are the bearing offsets from the homokinetic plane. These bearing, whichmay be a single bearing or multiple bearings, as described above,transmit torque from the input shaft S1 to the pivot point P1. Thesedimensions also represent an axial motion constraint on arms A1 and A2.During rotation of the joint, the distance from the end of A1 to axisC1, along axis AX1A remains generally constant. The same conditionapplies with respect to D2. Dimensions R1 and R2 represent the radialarm effective length as the distance between the pivot point P1 and theintersection of each arm rotational axis (AX1A and AX2A) with therespective shaft centerline, C1 and C2. In the illustrated embodiment,each arm segment length of a given arm pair is the same length, whichplaces the pivot point P1 within the homokinetic plane. A plane definedby shaft centerline C1 and arm effective length R1 is generallyperpendicular to a plane defined by the shaft centerline C1 and the armaxis AX1A. A similar orientation exists relative to arm effective lengthR2, shaft centerline C2 and arm axis AX2A.

The operation of the joint shown in FIG. 31A will be described inconjunction with a zero degree operating angle, unless otherwise noted.During operation, as the input shaft S1 rotates about axis C1, the axisAX1A rotates about C1 in a plane parallel to the homokinetic plane, PHK,as shown in FIGS. 31B-31D. Arm A1 is pivotally mounted and free torotate about axis AX1A. The arm A1 extends to the pivot point P1 and theentire arm, including the portion coupled to pivot pint P1, is capableof rotating about axis AX1A. As arm A1 rotates, pivot point P1 transfersboth motion and load to arm A2, which in turn, creates a torque onoutput shaft S2. In the illustrated embodiment, the center point Z0 is apivotal attachment of shafts S1 and S2 and constrains the shafts fromrelative axial motion. When the operating angle is zero degrees, axes C1and C2 form a straight line. As the shaft rotates through 360 degrees,point P1 rotates within the homokinetic plane, PHK. At a zero degreejoint angle, the homokinetic plane is generally perpendicular to theinput-output axis, C1-C2, as shown in FIGS. 31B-31D. As shown in FIG.31B, an operating angle of 30 degrees is visible from the top view,which defines the plane of the true joint angle. The operating angle θis the relative angular orientation of axis C1 to axis C2′. At angle,when shaft S1 is rotated through one revolution, the pivot P1 rotateswithin the homokinetic plane in the pattern of an oval or ellipse. Theorientation of the homokinetic plane, PHK, is at half of the joint angleθ, which defines the characteristic of constant velocity motion.

In another embodiment, the joint of FIG. 31A may include a second pairof arms identical to the first pair of arms A1 and A2. The second armpair may be oriented 180 degrees from first arm pair A1 and A2 and maybe coupled at a second pivot point that is opposite pivot point P1. Whenjoints are configured with 1 or 2 arm pairs, in one embodiment the inputand output shafts are pivotally connected together such that the jointis self supporting and the shafts are constrained from relative axialmovement. In another embodiment, the input and output shafts are notpivotally connected together and the shafts may be supported by externalstructures, such as pillow block bearings for example, that constrainthe relative axial movement of the joints. In yet another embodiment,three or more arm pairs may be oriented at generally equidistant radialangles from each other. With three or more arm pairs, the joint is selfsupporting and self centering which permits the shafts S1 and S2 to beeither pivotally connected together or free to move axially relative toone another to accommodate a plunge capability. The interconnectingpivots of the arm pairs all reside and rotate within the homokineticplane. Thus, the three arm pair joint can be configured to accommodatehigh operating angles and permit plunging capabilities.

Joint Design Considerations

As shown in FIGS. 32A, 32B, 34, 35, and 39, there are illustratedexamples of estimated load and performance tables and figures thatsupplement the following design points.

Loaded Areas of Consideration:

Design considerations of applied loading and friction are influential inthe areas of the spherical arm connection point and the arm base pivotwhich rides on the driver/driven hubs. In one embodiment, these bearingsmay be a maximum for the established swing envelope in order to reducebearing stress. As shown in FIG. 33, relative dimensions of bearings andarm thicknesses are tied to the swing diameter D. In one embodiment, thebearing diameter B may be defined as 0.25 D. An arm reference width, W,corresponding to the thinnest cross section area of the arm, may be 0.15D. An arm curvature angle, A may define the angular orientation of theinterconnecting pivot to the arm pivot base. The arm curvature angle A,determines the angle capability and static strength load capacity of thejoint. Various joint angles and arm curvature angles are shown in FIGS.34 and 35. As shown in FIG. 36, a pin plane separation distance, P,defines the spaced apart relationship of the arm bearing of an inputjoint portion to an output joint portion. In the illustrated embodiment,the pin plane separation is a function of the joint swing diameter D. Inone particular embodiment, the pin plane separation, P is 0.5 D when theinput and output joint sections are constrained by a single pointrotation device 1300. FIGS. 33 and 36 show first and second arm segments1302 and 1304 connected by an interconnecting pivot bearing element1306, similar to the various arm and arm segments described above. Thearm segment 1302 includes an inside radius 1308, at the thin section Wthat defines a surface intended to clear an arm pivot boss outerdiameter 1310. The amount of clearance between the inside radius 1308and the arm pivot boss outer diameter 1310 may create a contactcondition at a maximum joint angle. The arm segment 1302 further definesan outside radius 1312 at the thin section W that limits angulararticulation by contact with a central member 1314 and outer housing1316. The arm segment 1302 may be pinched on both sides as the jointangle increases to the maximum angle.

The strength of the arm segment 1302 is related to the cross sectiondefined at section W and the curvature angle A, shown in FIG. 33. Anincrease in the design of a maximum angle capability acts to increasethe curvature angle A and decrease the cross section at section W. Whenconsidering a design of the Harris joint, pivot bearing diameters, jointarm maximum angle capability, torque capacity, arm curvature and crosssection, and swing diameter are variables that are balanced to achieve asuitable structure. For example, for a given arm pivot bearing diameterand angle articulation capacity, increasing the swing diameter allows anincrease in arm strength. For a given material, the increase in strengthmay be exponential. The increase in strength is due, in part to anincrease in the cross sectional area at section W, a reduced curvatureof the arm, and a decreased solidity ratio. It should be noted that thesolidity ratio increases with decreasing joint diameter for a givenjoint torque capacity and arm bearing package size. It should also benoted that maximizing the torque capacity of the Harris joint in thesmallest envelope relies on maximizing the solidity ratio at the maximumoperating angle.

Spherical Arm Connection Point:

The spherical arm connection point is the interconnection point betweentwo torque transmitting arms. This point is permitted to rotate aboutits axis, have axial misalignment, and resist radial and axial loads. Inrelative terms, this connection point will withstand large amounts ofradial load and low to moderate amounts of axial load. When the Harrisjoint articulates it primarily rotates this connection about its axisand axial misalignment is minimal. In one embodiment, a sphericalbearing may be used, though consideration of friction is a designfactor. This consideration to address friction may include alternativelubricants, specialized low friction materials, rolling elements (i.e.,spherical bearings with ID lined needle rollers), and angulation limits

Arm Base Pivot:

The arm base pivot defines the connection between each pivot arm and thehub or central driving member. This connection point is configured topermit pivoting movement about an axis and resist axial and torsionalloading. Dependent upon the joint power density desired, the axial andtorsional loads at this connection point may become large. In oneembodiment, cylindrical needle bearings in combination with thrustroller bearing may be provided. Alternatively, specialized low frictionmaterials, such as for example polyamide-imide plastics may be used asthrust washer bearing elements. Additionally, ball bearings, which canresist both axial and radial loads may be used to reduce or eliminatethe need for a bearing combination. Other embodiments of bearingelements, such as tapered roller bearings, bushings, etc. may also beused.

Spacing the two needle bearings apart much as possible, within aparticular arm base portion, as can help to resist the torque anddecrease bearing stress. When a torque load is applied, the offsetcylindrical bearings are subjected to loads oriented in oppositedirections. In addition, the loading of these bearings is not uniformalong their length. Typically, the outside of the bearing is moreheavily loaded and the inside of the bearing will see a load thatdecreases to zero as it approaches the neutral axis.

Spatial Constraints:

As best shown in FIGS. 37A-D, and 38A-B, when the Harris jointarticulates as many as 6 of the 9 (for a 6 arm joint) connection pointsmove close together at the closed side or inside area of the joint. Inone embodiment shown in FIGS. 37A-37D, to provide an articulation angleof about 65 degrees, a ratio of joint swing diameter to the armconnection point diameter is about 4 to 1. Expressed differently, theindividual connection point diameter is approximately ¼ the total swingdiameter of the joint. In this embodiment, the spherical connectionpoint and arm base pivot areas that are about equal in diameter.

Bearing Optimization:

In designing the joint layout, it is desirable to space the arm basepivot bearings as far apart as practically allowable. Since bothbearings lie on the same side of the joint, the theoretical maximumspacing is about ½ of the joint swing diameter. This is a theoreticalvalue and includes assumptions that are not practical considerations. Inpractice, one embodiment of the joint may have a bearing spacing ofapproximately ¼ of the total joint swing diameter. A chart of exemplaryarm pivot bearing spacing relative to spherical bearing swing radius isshown in FIGS. 32A and 32B.

Harris Joint Design and Solidity Ratio Construction

For the various designs of the Harris joint, efficient packaging of thetorque transmitting components provides optimized designs that can bepackaged in space limited environments, such as an automotivepowertrain. At the outer bounds of packaging design, it is desirable tomaximize the articulation angle and torque capacity in the smallestpractical package. One design parameter is the torque density which isthe ratio of torque carrying capacity to joint swing diameter. Tomaximize torque density, the available volume within the joint swingdiameter is filled to its practical limit with structural material thattransmits torque. Filling the available volume with material makes eachof the components more rigid which promotes bearing alignment andmitigates rolling element pinching and skewing. We can refer to theavailable volume being filled with material as the solidity ratio of thejoint. For all practical purposes, the higher the solidity ratio thehigher the torque density. In addition to maximizing the solidity ratiofor designing an efficiently packaged CV coupling, proper designconsiderations that consider factors such as fatigue, notch sensitivity,desired manufacturing processes and resultant material structure shouldstill be followed. Designs that produce stress concentrations can reducethe efficiency of the structure. Achieving a high torque densityimproves packaging efficiency and makes the Harris joint competitive andrelevant when considering other devices that are currently used inapplications that require articulating torsional couplings (i.e. vehicledriveshafts). Due to the articulation of the joint and components thatswing through space, the joint ends up with localized areas of highcomponent density. These local regions are effectively what determinethe maximum solidity ratio.

In order to transmit a large torque in a small package, the firstcomponent to be considered and designed (i.e., analyzed and superimposedwithin the available joint interior space) are the pivot bearings of thepivot arm mounts and the spherical or interconnecting bearings at thepivot arm connection point. Design considerations will balance the unitloading of each bearing within practical limits. A drastic imbalance ofbearing strength may result in a weak link and premature failure or aninefficient design, meaning that one of the bearing areas is occupyingmore space than needed and decreases the available volume needed by theother bearings. If any of the bearings increase in diameter the othersare forced to decrease. In one embodiment, a design constraint may be toinclude a double shear connection, shown in detail in FIG. 11, whichsupports both sides of the pivot arm interconnection point and hasstrength and bearing stability advantages.

Once bearing types and diameters have been selected they can be placedin space with the joint at the maximum operating angle, as shown inFIGS. 37A-D. Hubs, illustrated in dashed lines, are shown for spatialreference. However, at this point in the design process the hubstypically have not been detailed. It should be noted that far less spaceis available for a joint that operates at high angle due to increasedlocalized component density. For high angle joints (i.e. 65 degrees orgreater) arm geometry is generally swept around other components toprovide clearance. This provides a tradeoff of strength and rigidity forincreased operating angle for a given swing diameter of the joint. Oncethe bearings have been placed in space at the maximum joint angle, thecomponents at the apex of the joint, where component density is highest,can be isolated. FIGS. 37A-D show the guide curves for a 65 degree jointthat represent the steps in joining the arm connection pivot to the armbase pivot. Two different arms are provided (quantity 3 each) for theparticular variant shown, one which includes a ring to hold the outerrace of the spherical bearing and another with a clevis to retain theball of the spherical bearing. It should be noted that the guide curvesfor an arm in a joint that articulates less will have less curvature andwill therefore be a more direct path resulting in a stronger and morerigid arm. FIGS. 38A and 38B provide a reference for how the armgeometry changes for a 20 degree joint versus a previously shown 65degree joint. Despite the fact that more space is available and morematerial can be used for a low angle joint, there is a tradeoffregarding the total mass of the components and their strength/rigidity.Once the arms have been designed and their sweep has been determined, ahub which provides clearance for them can be designed. A hub thatprovides minimal clearance to the sweeping arms will result in theshortest axial length possible.

The principle and mode of operation of this invention have beenexplained and illustrated in its preferred embodiment. However, it mustbe understood that this invention may be practiced otherwise than asspecifically explained and illustrated without departing from its spiritor scope.

What is claimed is:
 1. A constant velocity coupling comprising: adriving central shaft having a plurality of pivot arm mounting boresthat are each offset along an axial axis; a plurality of driving pivotarms, each having a pivot mount and an interconnecting end, the pivotmount of each pivot arm is pivotally connected to the driving centralshaft at the plurality of pivot arm mounting bores such that theplurality of interconnecting ends are aligned in a homokinetic plane; adriven central shaft having a plurality of pivot arm mounting bores thatare each offset along an axial axis; a plurality of driven pivot arms,each having a pivot mount and an interconnecting end, the pivot mount ofeach pivot arm is pivotally connected to the driven central shaft at theplurality of pivot arm mounting bores such that the plurality of linkreceivers are aligned in the homokinetic plane; and an interconnectingbearing element coupling each of the driving and driven pivot armstogether such that torque and rotary motion are transmitted through ajoint angle.
 2. The constant velocity coupling of claim 1 wherein thedriving and driven interconnecting ends are configured as linkreceivers, and the interconnecting bearing element is configured as aclevis pivotally coupled to a hinge link, the clevis and hinge link eachbeing supported for rotational movement within the corresponding linkreceiver.
 3. The constant velocity coupling of claim 1 wherein thedriving and driven interconnecting ends are configured as a sphericalbearing element and a connecting bore.
 4. The constant velocity couplingof claim 1 wherein the plurality of driving and driven pivot arms eachdefine complementary curvatures associated with adjacent arm pivotconnections that define a maximum joint angle capacity within a jointswing diameter.